Problem: $9$ is what percent of $10$ ?
Solution: Having a percent of something means that you get that percent out of every $100$ We can set up a proportion to find out what percent of $10$ we need to take to get $9$ $ \dfrac{{\text{percent}}}{100} = \dfrac{{\text{part}}}{{\text{whole}}}$ Which things do we know, and what are we trying to find? We are trying to find the ${\text{percent}}$ . Is $10$ the ${\text{part}}$ or the ${\text{whole}}$ The $10$ is the ${\text{whole}}$ . This means the ${\text{part}}$ is $9$ $ \dfrac{{\text{percent}}}{100} = \dfrac{{9}}{{10}}$ If we multiply the denominator of the fraction on the right by $10$ , it will be the same denominator of the fraction on the left. To keep things equal, let's also multiply the numerator on the right by $10$ $ \dfrac{{\text{percent}}}{100 } = \dfrac{{9 \times 10}}{{10 \times 10}}$ $ \dfrac{{\text{percent}}}{100 } = \dfrac{{90}}{{100}}$ $ {\text{percent}} = {90}$ So $9$ is $90\%$ of $10$.